The present invention relates to nozzle flow thrust vector measurement, and more particularly to nozzle flow thrust vector measurement in a nozzle flow thrust vector bench.
Aircraft jet and rocket engine thrust measurements can be carried out by mounting a test nozzle on a test stand. The test nozzle may be, for example, a 1:14 scale model of a full-size nozzle of which characteristics are to be tested. In accordance with current approaches, such test stands are supported by load cells that measure thrust forces exerted as a result of propulsion gases emitted by the nozzle. The thrust forces generated result in strains developed in the load cells themselves that are transduced into electrical quantities to provide an indication of the thrust forces being exerted by the test nozzle on the test stand as a result of the emission of the propulsion gases from the test nozzle.
For nozzle flow thrust vector measurements, it is desirable to provide an indication of any force components generated, be they in a forward direction (along a thrust axis, or z-axis), or side directions (normal to the thrust axis, or along a y-axis for pitch and along a x-axis for yaw). (Forces in side directions result, for example, when a direction of thrust is out of alignment, either intentionally or unintentionally with the thrust axis of the nozzle itself.) The force component in the forward direction and the force components in the side directions may be measured by suitable load cells coupled to the test stand, with each load cell having a load sensitive axis suitably oriented such that together the load cells provide an indication of the force component in the forward direction and the force components in the side directions.
When test nozzles with on-board propulsion, such as rocket motors or complete Jet engines, are tested the use of a test stand is possible, because the only forces the test stand "sees" are those generated by the emission of the propulsion gases. Problematically, however, when small-scale models are employed, without on-board propulsion, propulsion gases must be supplied to the test nozzles from an external source. Heretofore no adequate solution has been available to the elimination of forces applied by external propulsion gas supplies to the test nozzle and in-turn to the test stand. As a result, test stands have not been satisfactory for many nozzle flow thrust vector measurements.
In another, and heretofore preferred, approach to thrust measurements, a wind tunnel sting may be employed to measure nozzle thrust. Wind tunnel stings are six-component thrust measuring devices employing strain gauges attached to a horizontal metal tube. In practice, the test nozzle is positioned on (i.e., mounted on) the metal tube, and thrust forces generated by propulsion gases escaping the test nozzle are transferred to the metal tube and thus to the strain gauges.
Wind tunnel stings are installed in most major wind tunnels at research institutions, such as universities, government sponsored laboratories and government research agencies, and are designed specifically for measuring thrust vectors generated by model aircraft output nozzle flow in a wind tunnel environment. Unfortunately, these wind tunnel stings are located in awkward horizontal positions in test sections of wind tunnels.
Wind tunnel stings are very expensive, and in fact prohibitively expensive for many researchers who would benefit from their use. For example, it is expected that the cost of a wind tunnel sting, without the ability to attach a test nozzle for nozzle flow thrust vector measurements, would be in excess of $100,000 (at the time of filing of this patent document). If one were to add nozzle flow thrust vector measurement capabilities, such a wind tunnel sting would exceed $500,000 or more in costs.
The present invention advantageously addresses the above and other needs.